Many devices are designed to operate at more than one frequency range. For example, for wireless local area networks (WLANs), the IEEE 802.11b and IEEE 802.11g standards operate in the IEEE 2.4 GHz range, while the IEEE 802.11a standard is for operation in the 5 GHz band. There are now many IEEE 802.11 devices that operate in both frequency bands, e.g., devices that include two radios that can operate simultaneously, one in the 2.4 GHz band and one in the 5 GHz band. In order to take advantage of diversity, each radio requires at least two antennas or a diversity antenna that includes at least two antennas deployed in the same enclosure.
Thus, it is desirable to have a dual band antenna. There are several dual band antennas on the market aimed at dual frequency WLAN devices. Two examples are the Cushcraft (Cushcraft Corporation, Manchester, N.H.) model S24493DS diversity dual band low profile omnidirectional antenna and the PCTel MC24580304PT single dual band antenna (PCTel Inc., Chicago, Ill.). PCTel also has model Z2452 that is a dual band (single) short omnidirectional antenna. These Cushcraft and PCTel antennas are for operation in the 2.4 GHz and 5 GHz bands.